Recent advances in high speed integrated circuit technologies enable various innovative and versatile applications through an ultra-low-power wireless link such as mesh sensor network, a remote industrial monitoring and an implantable medical device. For the wireless data access, the modulation scheme adapted is critical to the link qualities in terms of bit rate and bit error rate.
Phase shift keying (“PSK”), specifically binary phase shift keying (“BPSK”) and quadrature phase shift keying (“QPSK”), is a widely used digital modulation scheme in wireless systems such as IEEE 802.15.4, global positioning system (“GPS”), IEEE 802.11 (“WiFi”) systems and medical telemetry. This technique represents digital bits by shifting the phase of the carrier signals. Under similar bandwidth occupation, PSK signals are more robust to noise as compared to amplitude shift keying (“ASK”) or frequency shift keying (“FSK”) modulation schemes.
Demodulation of a PSK signal usually requires coherent detection and synchronization which is accomplished by a carrier recovery circuit such as a COSTAS loop. Due to its complexity, however, the room for power consumption reduction of COSTAS loop is limited. This has become a roadblock to further advancements. Accordingly, major developments are needed and would be of significant benefit.